#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	double sum = 0;
	int flag = 1;
	for (int i = 1; i <= 100; i++)
	{
		sum += 1.0 / i * flag;
		flag = -flag;
	}
	printf("%lf\n", sum);
	return 0;
}